A digital image is made up of many pixels that are represented in a computer system as digital values. The pixels are typically arranged in columns and rows such that the collected pixels form images to be perceived by a user. Pixels can be displayed as color or gray-scale images (also called black and white images). In a gray-scale image, each pixels is represented by a luminance (also called intensity) value. For example, where luminance is expressed using eight digital bits, each pixel is represented by a single unsigned byte with a range of 0 to 255, where 0 specifies the darkest pixel, 255 specifies the brightest pixels, and intermediate values specify intermediate luminance. Moreover, images can be represented in color format wherein chrominances and luminances are specified. Chrominance (or color) can be represented using a collection of colors that when mixed together generate a perceived color. For example, the colors red (R), green (G), and blue (B) can be used to display many different colors. Depending on the chromatic content of the individual colors, a color gamut is available from which colors can be generated.
Digital image technology finds many applications including television, video and computer graphics. In these types of applications, it can be straightforward to display any given image; however, many possibilities exist when it becomes necessary to display two or more images over the same display area. Whereas to display either of two images as if it were placed on top of the other can be a simple task, it can, however, be the case that a mix or blending of the images is necessary. In the field of art to which it pertains, this mixing or blending is often achieved through a technique called alpha blending. Through the use of alpha blending, two or more images can be individually displayed, but can also be partially displayed with one image dominating the other.
In computer graphics applications, for example, in computer games, blending of images is very important, however, for complex or fast-paced graphics, alpha blending calculations can become computationally intensive. In certain applications, a screen can contain millions of individual pixels where each pixel must be refreshed every 1/60th of a second. Moreover, many or all such pixels may require alpha blending calculation. Thus, there is a need for a method for fast alpha blending calculations in systems incorporating complex digital graphics. There is a further need for an apparatus that can produce fast alpha blending calculations through reduced hardware or reduced complexity hardware, software, or firmware.